Means for indicating phase



MEANS FOR INDICATING PHASE Filed April 21, 1958 EG. l.

.atl

Inventor Irvingy Wolff Patented Dec. 3, 1940 UNITED STATI-:s

PATE/NT OFFICE MEANS FOR INDICATINGPHASE l Delaware Application April 21, 1938, Serial No. 203,358

2 Claims.

My invention relates to a means for indicating the relative phase displacement of two alternating voltages of the same frequency. which is equivalent to a determination of the time inter- 6 val between the occurrence of the two voltages.

It is well known that in many applications in the radio art it isJ desirable or necessary to determine the relative phase of two voltages. A great many procedures have been devised to accom- 10 plish this purpose. However, I am not aware of any means which accomplishes this end in as simple a manner as that which is proposed by this invention. A vacuum tube having at least two grids, a direct current meter, a capacitor, two

resistors, and the usual power supply for energizing the tube, when connected in the manner of my invention, are suiilcient to indicate phase difference.

Itis, therefore, an object of my invention to 2o provide a means for indicating the phase displacement `between two alternating voltages. l It is a further object of my invention `to provide a simpliiled apparatus for indicating phase displacement of two voltages.

A still further object isto provide means i'or indicating the time interval between theoccurrence of two voltages of the same frequency which differ in phase.

This invention4 win be better understood from" the following description when considered in connection with the accompanying drawing, and its scope is indicated by the appended claims.l

Referring to the drawing. l

- Figure 1 is a schematic diagram of an embodiment of my invention,

Figures 2 to-7 represent various voltage and current relations characterizing the operation of my device, and

Figure 8 is an alternative connection of a. portion of Fig. 1.

Referring to Fig. l, I have shown two sourcesof voltage, l and 3, whose phase is to be measured. 'Ihese voltages are preferably equal in value, but may be of any desired frequency. They may be derived in any desired manner, as by demodulation of a radio frequency carrier, taken from various stages of an audio amplifier. or the like.

The output of source i of the'first voltage A 2S through a biasing battery 35.

(Cl. Plz-245) ing network il, whose purpose will be explained later. The output of the network is connected to the one end of the resistor i3. The circuit of the phase reversing network il has not been shown in detail as itis Well known to those skilled 5 in the art.

A series-connected capacitor 45 and resistor 43 and a voltmeter 8 are connected across the output of the source 301 the secondvoltage of phase. B.

' The remaining end of the resistor 43 is grounded. l0

The output terminal is also connected rto terminal 39 of a two-way phase indicating switch 31. 'I'he point of junction ofthe resistor 43 and capacitor 45 is connected to the remaining terminal 4| of the phase-indicating switch 3l. The selector arm 15 is connected through a resistor I5 to the second grid i9 of the vacuum tube 2|. y

A connection is made from l the anode y 23 through a D. C. microammeter 25 to a sourceof anode potential 29. @A capacitor 2l may bygo pass thismeter. A cathode 3l is connected to ground and tothe negative terminal of battery V The cathode may be heated by alament 33 connected to a source of current which is not shown.

, While the vacuum tube 2| may be any one of a great variety of multi-grid tubes, it is preferably of the coplanar type,having cathode, anode. and two interlaced grids symmetrically and equally positioned with respect to 'the cathode 30` and anode. Interlaced coplanar grids give a more uniform` result due to the equal eiiect of equal voltages on each grid.

The operationof the device which illustrates my. invention may best be explained by reference 35 to the voltage and current curves shown in Figs.

2 to 7. Fig. 2 represents one cycle'of a voltage applied tothe grid of a vacuum tube and the corresponding plate current which results. In this ligure, a low grid circuit impedance is aso sumed. During the positive half of. the grid voltage cycle, grid current will be drawn. 'If now a high resistance is placed between the source of grid voltage rand the grid itself, as shown in Fig.

1, the grid voltage will be limited by the resistor 5 due to the drop through it caused by the grid current. The result is that the grid voltage, and consequently the anode current, will quickly reach a maximum value. This'is shown in Figure 3 in which the shaded portion represents the timel during which substantially uniform anode .cur-

rent ilows, and the dotted line represents the source voltage, which is limited in the positive half cycle as shown by the solid voltage line.

One characteristic oi' an interlaced coplanar u grid vacuum tube is that substantially no anode current can flow if either grid is' suili'ciently negvals in which both grids are above the cut-ofi value of the tube. 1 In order to have the cut-oil? grid voltage occur` as `near zero bias'as possible, the anodes are preferably operated at a low positive potential.

Fig. 4 shows two voltages whose phaseA angle is less than 90. The phase is represented by the time displacement At. As shown in this ligure, very little anode current ows when either one or both of the grids are negative. l

Fig. 5 is similar to Fig. 4 except the phase now approaches 180. The time'displacement At nas increased and the period during which anode current flows has proportionately decreased.

` by decreasing meter readings.

It is obvious that, when the two voltages are exactly out of phase, substantially no a'node current will flow, for one oi?V the grids will `be vnegative substantially throughout the entire cycle. Figs. 6 and 7 represent successively greater phase angles between and 360. It willbe noted that the interval during which anode currentA flows-is now increasing, and is inereasingwith an increase in the time displacement At.

It may thus be seen that, by'limiting the grid voltage as shown in Fig. 1, for example, substantially constant 'anode current lmay be made to flow during periods directly or inversely proangle, of the applied voltages. If a meter is placed in the anode circuit and by-passed by a capacitor, it will integrate the anode current impulses and will indicatean anode current Awhich is directly or inversely proportional tothe phase angle of -the applied voltages, depending upon whether the phase of the voltages is between 180 and 360 or between 0 and 180. Consequently,

the meter 25 can be calibrated in terms of phase angle, time displacement,V or `other factorhdepending upon its desired use.

two voltages which have a fixed predetermined value. Output voltmeters l and 6 are convenient for this purpose. f Y

If it is desirable to have an increasing reading with increasing phaseangles between 0 and 180, the phase reversing network Il may be introcreasing readings on,the meter,vand increasing phase angles between 180 and 360 are indicated For greatest racg curacy, -it is preferable to operate the device byv It will be noted that equal phase displacements above and below 180 are indicated by the same shown in connection with switch 31 at the outputv of the source 3' of voltage B. By placing the selector switch at positionl 4I, the phase of the applied voltage is advanced. The -degree oi shift may be chosen by properly selecting the values oi the capacitor 45 and resistor 43. The switch 31 may conveniently take'the form of a push button.- Since it shifts one-of the voltages in a known direction, the-quadrant may be determined by noting whether the anode current increases or decreases. g

The foregoing specification and drawing ar merely illustrative of Amy invention. Numerous modiilcations within the scope of my invention will occur vto those skilled in the art. For example, the phase-indicating switch 31 may have a number of contacts, or a variable phase device may be used which will permit a wider adjustment. It might be desirable to connect an inductor 46 in a similar manner. in place of the capacitor 45, as shown in Fig. 8. This connection makes possible the selection of a lagging voltage to aid in the determination of quadrant. While sine wave voltages have been illustrated, this indicator will respond to voltage waves of other spective grid electrodes, means forcausing the4 amplitude ofsaid anode current to vary asl a linear function of the phase angle between said alternating voltages, and indicating means responsive to said anode current.

1 2. A linear direct reading phase meter comprising a thermionic tube having cathode, anode and at least two grid'electrodes, means for applyfing alternating voltages between said cathodes and respective grid electrodes, limiting means in circuit with said grid electrodes for causing thev y,.a'mplitude of said anode current to vary as a duced into the circuit to shift one of the applied In such case, increasing phase linear function of the` phase angle between said alternating voltages, and a current responsive meter connected in circuit withsaid anode electrode, the deilection oi' said meter being a linear function of said phase angle.

' IRVING WOLFF.' v 

